Corn Genetic Mapping Helping Researchers

ARS is tapping into corn's tropical diversity.

Sep 15, 2010

Using genetic mapping, scientists at USDA believe the genetic diversity of tropical maize could be used to improve maize varieties in temperate regions of the United States. But because tropical varieties flower very late when grown under long day lengths in temperate climates, undesirable traits such as poor yield can mask favorable traits such as disease resistance.

A team led by Jim Holland, a plant geneticist at the ARS Plant Science Research Unit in Raleigh, North Carolina, has identified four regions, or quantitative trait loci, in the maize genome associated with photoperiod sensitivity. The QTLs represent 2% of the genetic map, showing that the scientists have sufficiently narrowed the genome.

"Tropical maize possesses genetic diversity that could be used to improve maize in temperate regions, such as the United States," explains Holland. "But because tropical maize flowers very late when grown under long day lengths, undesirable traits such as poor yield can mask other favorable traits such as disease resistance. Our goal is to better understand the mechanisms behind photoperiod sensitivity so we can access the genetic diversity of tropical maize more easily."

The results of this work will help researchers select for genes in hardy tropical varieties that could make them better adapted to the long day lengths of temperate regions. They may also help U.S. breeders develop corn varieties that offer increased yields, disease resistance and other desired traits.